1. Field of the Invention
The present invention relates to a drilling head for the controlled operation of a drill string and, in particular, to a pump ring for maintaining circulation of lubricant through the bearing chamber of the drilling head.
2. Description of the Prior Art
Drilling heads are extensively used in drilling operations to prevent drilling fluids from flooding the rig floor by diverting such fluids. The drilling head typically incorporates at least one stationary or rotating stripper rubber which seals against the drill string to prevent drilling fluid from flowing through the axial passage of the drilling head. A drive assembly mounted in the upper end of the drilling head controls the rotation of the drill string and may include a kelly drive and a drive bushing. Associated with the drive assembly are bearings mounted in a bearing chamber. In order to lubricate the bearings while dissipating head generated in the operation of the drilling head, a remote lubricant pump and reservoir are mounted in fluid communication with the bearing chamber. Such lubricant systems typically include a supply line connected to the drilling head at one end of the bearing chamber and a return line connected to the other end of the chamber forming a lubricant circulation path. Lubricant pumped to the bearing chamber, lubricates and cools the bearings and returns to the reservoir.
Circulation of lubrication fluids is dependent upon continuous operation of the pump associated with the lubricant supply. However, if the pump fails or becomes clogged, lubricant supply will be interrupted resulting in damage to the bearings or more extensively to the drilling head. While the bearings are replaceable, repair of the drilling head and the associated downtime can add significantly to the cost of drilling operations. One solution is the addition of a back-up pump or an alarm system which signals the interruption of lubricant flow. However, these alternatives also add to the cost of drilling operations.